How to check if session is set?

I'm using Symfony 3.

class UserProfileSubscriber implements EventSubscriber
{

    public function __construct(EntityManagerInterface $em)
    {
        $this->em = $em;

    }

    public function getSubscribedEvents()
    {
        return array(
            SecurityEvents::INTERACTIVE_LOGIN => 'interactiveLogin',
            KernelEvents::REQUEST => 'request',
        );
    }

    public function interactiveLogin(InteractiveLoginEvent $event, EntityManagerInterface $em)
    {

        $user = $this->em->find(User::class, $userId);
        if (!$user->getStreetAddress1())
        {
            $session = $event->getRequest()->getSession();
            $session->set('userNeedsProfileUpdated', true);
        }
    }

    public function request(KernelEvent $event)
    {

        $session = $event->getRequest()->getSession();
        $session->get('userNeedsProfileUpdated');
        if($session->has("userNeedsProfileUpdated")) {
            $event->setResponse(new RedirectResponse('user_profile'));
        }
    }
}

How do I check if "userNeedsProfileUpdated" is set to true in the session? I'm using the has method, but I'm not sure I'm using it right. Then set it to false to prevent a loop.

I need to listen for logins and then check if certain fields in my form are set, if they aren't redirect to the form view page.

I'm not sure my code is correct so far.

Thanks